Consider the following two specifications of a model: library( splines ) x <- 1:100 y <- rnorm( 100 ) w <- rep( 1, 100 ) A <- factor( sample( 1:2, 100, replace=T ) ) B <- factor( sample( letters[1:4], 100, replace=T ) ) summary( lm( y ~ ns( x, knots=c(30, 50, 70 ), intercept=T ):A - 1 + B ) ) summary( lm( y ~ ns( x, knots=c(30, 50, 70 ), intercept=T ):A - 1 + B:w ) )
The interaction with the constant variable w is how I got to have the two spline terms as "proper" intercept terms. Is there another way to do this, or is it a featur of the model formulae that lower order terms appear before higher order terms regardless of the order they are specified in the model? Bendix Carstensen ---------------------- Bendix Carstensen Senior Statistician Steno Diabetes Center Niels Steensens Vej 2 DK-2820 Gentofte Denmark tel: +45 44 43 87 38 mob: +45 30 75 87 38 fax: +45 44 43 07 06 [EMAIL PROTECTED] www.biostat.ku.dk/~bxc ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
